Liang Yao-Yun, Brunicardi F Charles, Lin Xia
Michael E. DeBakey Department of Surgery, Baylor College of Medicine, BCM-390, Research Tower, Room R711, One Baylor Plaza, Houston, TX 77030, USA.
Cell Res. 2009 Jan;19(1):140-8. doi: 10.1038/cr.2008.321.
Id1 is a member of the inhibitor of differentiation (Id) protein family that regulates a wide range of cell functions. Previous studies have shown that expression of the Id1 gene is down-regulated by TGF-beta in epithelial cells, whereas it is up-regulated by BMP in a variety of cell types. During our study of the biological function of TGF-beta1, we found that Id1 can be strongly up-regulated by TGF-beta1 in the human mammary gland epithelial cell line MCF10A. Quantitative real-time RT-PCR has revealed as high as 7.5-fold induction of Id1 mRNA by TGF-beta1 in MCF10A cells after 1 h of TGF-beta1 stimulation, and this induction does not require de novo protein synthesis. Using Smad knockdown and knockout approaches, we have identified Smad3 as the responsible R-Smad for mediating transcriptional activation of the Id1 gene. Chromatin immunoprecipitation assay confirms that Smad3 and Smad4 bind to the upstream region of the Id1 gene. Our results demonstrate that Smad3, but not Smad2, mediates TGF-beta1-dependent early transcriptional induction of Id1.
Id1是分化抑制（Id）蛋白家族的成员，该家族可调节多种细胞功能。先前的研究表明，Id1基因的表达在上皮细胞中被转化生长因子-β（TGF-β）下调，而在多种细胞类型中被骨形态发生蛋白（BMP）上调。在我们对TGF-β1生物学功能的研究中，我们发现Id1在人乳腺上皮细胞系MCF10A中可被TGF-β1强烈上调。定量实时逆转录聚合酶链反应（RT-PCR）显示，在TGF-β1刺激1小时后，MCF10A细胞中Id1 mRNA的诱导高达7.5倍，并且这种诱导不需要从头合成蛋白质。使用Smad基因敲低和敲除方法，我们确定Smad3是介导Id1基因转录激活的相关R-Smad。染色质免疫沉淀分析证实Smad3和Smad4与Id1基因的上游区域结合。我们的结果表明，介导TGF-β1依赖性Id1早期转录诱导的是Smad3，而非Smad2。
